Question: Which of the following numbers is a multiple of 5? ${43,46,49,72,80}$
The multiples of $5$ are $5$ $10$ $15$ $20$ ..... In general, any number that leaves no remainder when divided by $5$ is considered a multiple of $5$ We can start by dividing each of our answer choices by $5$ $43 \div 5 = 8\text{ R }3$ $46 \div 5 = 9\text{ R }1$ $49 \div 5 = 9\text{ R }4$ $72 \div 5 = 14\text{ R }2$ $80 \div 5 = 16$ The only answer choice that leaves no remainder after the division is $80$ $ 16$ $5$ $80$ We can check our answer by looking at the prime factorization of both numbers. Notice that the prime factors of $5$ are contained within the prime factors of $80$ $80 = 2\times2\times2\times2\times5 5 = 5$ Therefore the only multiple of $5$ out of our choices is $80$. We can say that $80$ is divisible by $5$.